Some tracked vehicles, such as bulldozers and tanks, have devices known as bogies as external suspension components. A bogie is a chassis or framework carrying wheels that is attached to a vehicle. The bogie can be fixed in place with respect to the vehicle with the wheels being mounted on a pivoting arm, as on a cargo truck, mounted on a swivel, as on a railway carriage or locomotive, or sprung as in the suspension of a caterpillar tracked vehicle. The bogie has two or more rollers or wheels and some type of sprung suspension to smooth the ride across rough terrain.
One example of bogies for a track-type tractor is shown in U.S. Pat. No. 4,152,031, issued May 1, 1979 to Maguire, is an example of a rotatable shaft and roller assembly. In the Maguire patent, each bogie has a pair of rollers connected to each other by an arm, and the arm in turn is pivotally connected to the bogie frame by a shaft or pin. As the tractor moves over the surface and encounters a bump or other obstruction over which the tracks must pass, the forward roller first engages the obstruction and moves upwardly. The shaft of the bogie moves upwardly by a lesser distance such that the upward shock to the tractor transmitted by the bogie is less if the front roller were attached to a fixed axle. Eventually, the shaft moves upwardly to the full distance need to pass over the obstacle after the rearward roller is engaged by the obstacle.
The Maguire patent provides an illustration of a shaft assembly for the rollers of the bogie that may similarly be implemented as the shaft or pin about which the arm pivots. A shaft mounted to the bogie frame includes an opening leading to an internal cavity of the shaft. Sleeve bearings are disposed about the outer surface of the shaft, and the roller is mounted about the sleeve bearings and held in place by lateral retaining rings. The shaft includes a pair of bores extending radially from the inner surface defining the cavity to the outer surface of the shaft. A lubricating fluid is added to the cavity through the opening of the shaft, with a resilient plug being inserted into the opening to retain the fluid therein. As the roller and sleeve bearings rotate together about the shaft, the fluid circulates between the cavity and the outer surface of the shaft through the bores to keep the interface between the shaft and the sleeve bearding lubricated.
In arrangements such as that shown in the Maguire patent, the lubricating fluid is critical for the bogie to operate for the duration of the designed useful life. In some implementations, however, the resilient plug can pop out of the opening, thereby allowing the lubricating fluid to drain and causing the bogie to rapidly fail due to the increased friction between the moving parts. The resilient plugs may be pushed out of the opening due to internal pressure within the cavity, or may be dislodged by debris external to the shaft. In many implementations, space limitations may preclude merely placing a cover over the end of the shaft that will retain the plug within the opening. Therefore, a need exists for a new technology for retention of a plug for a shaft in a bogie arrangement that may allow pressure to build within a cavity of the shaft without the plug being forced out to release the lubricating fluid within the cavity.